Includes bibliographical references ( p. 225-231.)

I - Introduction - Physical features - General geology of the Palomb e Plain - Basement complex rocks - V - Dolerite dykes - VI - Fenitizati on - VII - Nephelinization - VIII - Early Nephelinite and melanephelini te dykes - IX - Agglomerate, trachyte and feldsphatic - X - Sovite-aggl omerate and sovitic dykes of the first ring-stucture - XI - Agglomerate , apatite-rock, and carbonatites of the second ring - structure - XII - Nepheline - syenite and Ijolite - XIII - Carbonate - silicaterocks ass ociated with the foyaitic ring-dyke - XIV - Alkaline dykes - XV - Late dykes and plugs of melanephelinite and olivine - melanephelinite - XVI - Beforsites and beforistic lamphrophyes - XVII - Fault pattern - XVIII - Lacustrine, colluvial and eluvial deposits - XIX - Structure and str ess pattern of the ring-complex - XX - Trace element disttribution - XX I - Petrogenesis of carbonatites ad assoiated rocks - XXII - Economicge ology - .